diff --git a/main/src/main/scala/sbt/internal/Repository.scala b/main/src/main/scala/sbt/internal/Repository.scala
index 51195f9a2..7d0b0f82f 100644
--- a/main/src/main/scala/sbt/internal/Repository.scala
+++ b/main/src/main/scala/sbt/internal/Repository.scala
@@ -33,7 +33,7 @@ import scala.collection.JavaConverters._
  * @tparam K the key type
  * @tparam V the value type
  */
-trait Repository[M[_], K, V] extends AutoCloseable {
+private[sbt] trait Repository[M[_], K, V] extends AutoCloseable {
   def get(key: K): M[V]
   override def close(): Unit = {}
 }